[A histological study on osteosarcoma. Part I: Relationship between modes of osteoid formation and differentiation of tumor cells].

This study was undertaken to clarify whether the osteoid forming activity seen in osteosarcoma can be used as an index to show the degree of differentiation of the tumor. Twenty six human osteosarcomas which had been amputated in our clinics were used in this study. The whole slice of the primary tumor was stained by HE and Masson stain. The following observations were microscopically made in the peripheral, transitional and central part of the tumor; 1) the content and maturity of osteoid, 2) the degree of polymorphism and mitotic activity of the tumor cells. In 13 out of 26 cases, the amount and maturity of osteoid gradually increased toward the center of the tumor. On the other hand, the degree of polymorphism and mitotic activity of tumor cells in these cases gradually decreased toward the center. Mitotic activity in the center of the tumor decreased to about half of the peripheral part. The clinical courses of these 13 cases were milder than those in which the gradual increase of the amount and maturity of osteoid toward the center of the tumor were not observed. These results showed that zone formation of osteoid maturity in osteosarcoma can be used as an index to show the degree of differentiation of the tumor.